Before that, promoted tweets had appeared only in search results and on the top of the Twitter trends lists.

The new system means that Twitter users can be served adverts from a company in their personal timelines, regardless of whether they follow the brand.

A spokesman said: “This will be the first time that consumers will be exposed to adverts in their timelines from brands they don’t follow. Initially, we will make this feature available to a single-digit percentage of our global user base.

“Of this group, we will only show promoted tweets to people from advertisers relevant to their interests. We are carefully measuring how users respond to and engage with these Tweets; based on this response, we will roll this capability out to a wider audience in the coming months.”